IMO, machamp and gallade are just as useful, but different.
Machamp is much bulkier and has the ability to virually cripple any non-ghost switch in with no-guarded dynamic punch. Every pokemon hates being confused, regardless of whether they resist the attack or not. Guts versions are obviously great status absorbers.
Gallade is good because it's somewhat faster, but also because it gets more diverse attacks. For example, psycho cut, night slash, etc. while retaining machamp's access to the elemental punches.